// SPDX-License-Identifier: GPL-2.0
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/*
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* Network Checksum & Copy routine
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*
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* Copyright (C) 1999, 2003-2004 Hewlett-Packard Co
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* Stephane Eranian <eranian@hpl.hp.com>
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*
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* Most of the code has been imported from Linux/Alpha
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*/
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#include <linux/module.h>
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#include <linux/types.h>
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#include <linux/string.h>
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#include <net/checksum.h>
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/*
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* XXX Fixme: those 2 inlines are meant for debugging and will go away
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*/
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static inline unsigned
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short from64to16(unsigned long x)
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{
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/* add up 32-bit words for 33 bits */
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x = (x & 0xffffffff) + (x >> 32);
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/* add up 16-bit and 17-bit words for 17+c bits */
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x = (x & 0xffff) + (x >> 16);
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/* add up 16-bit and 2-bit for 16+c bit */
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x = (x & 0xffff) + (x >> 16);
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/* add up carry.. */
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x = (x & 0xffff) + (x >> 16);
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return x;
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}
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static inline
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unsigned long do_csum_c(const unsigned char * buff, int len, unsigned int psum)
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{
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int odd, count;
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unsigned long result = (unsigned long)psum;
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if (len <= 0)
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goto out;
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odd = 1 & (unsigned long) buff;
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if (odd) {
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result = *buff << 8;
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len--;
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buff++;
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}
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count = len >> 1; /* nr of 16-bit words.. */
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if (count) {
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if (2 & (unsigned long) buff) {
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result += *(unsigned short *) buff;
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count--;
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len -= 2;
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buff += 2;
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}
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count >>= 1; /* nr of 32-bit words.. */
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if (count) {
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if (4 & (unsigned long) buff) {
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result += *(unsigned int *) buff;
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count--;
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len -= 4;
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buff += 4;
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}
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count >>= 1; /* nr of 64-bit words.. */
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if (count) {
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unsigned long carry = 0;
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do {
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unsigned long w = *(unsigned long *) buff;
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count--;
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buff += 8;
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result += carry;
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result += w;
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carry = (w > result);
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} while (count);
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result += carry;
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result = (result & 0xffffffff) + (result >> 32);
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}
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if (len & 4) {
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result += *(unsigned int *) buff;
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buff += 4;
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}
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}
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if (len & 2) {
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result += *(unsigned short *) buff;
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buff += 2;
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}
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}
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if (len & 1)
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result += *buff;
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result = from64to16(result);
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if (odd)
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result = ((result >> 8) & 0xff) | ((result & 0xff) << 8);
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out:
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return result;
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}
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